Recently, in mobile communication systems such as mobile phones, mobile communication terminals have been strongly requested to have a smaller size and lower power consumption. In order to achieve these requests, it is necessary to reduce ON-resistance Ron and OFF-capacitance Coff in an antenna switch, for example. One example of a device that is currently put into practical use for such an antenna switch is a junction pseudo-morphic high electron mobility transistor (JPHEMT).
The JPHEMT is a semiconductor device that performs current modulation utilizing a PN junction and a heterojunction. Such a semiconductor device includes, for example, a heterojunction between a channel layer made of InGaAs and a barrier layer (AlGaAs) made of AlGaAs having a wider bandgap than that of the channel layer (InGaAs). Inside the barrier layer (AlGaAs), a second low resistance region containing impurities of a reverse electrically conductive type is provided on a surface layer opposite to the channel layer, and a gate electrode is coupled to the second low resistance region. Further, inside the barrier layer (AlGaAs), a carrier supply region containing impurities that serve as carriers is provided closer to the channel layer than the second low resistance region. Further, a source electrode and a drain electrode are ohmic-bonded to the barrier layer (AlGaAs) on both sides of the second low resistance region and the gate electrode.                In the semiconductor device configured as described above, a two-dimensional electron gas layer in which electrons serving as carriers are confined at high concentration is formed at an interface, in the channel layer, on side of the barrier layer. By applying a voltage to the gate electrode to control the concentration of the two-dimensional electron gas layer, a current is modulated that flows between the source electrode and the drain electrode via the channel layer portion below the second low resistance region (see, e.g., PTL 1 listed below for the above description).        